1. Field of the Invention
The present invention relates to a housing structure of an acoustic controller, and more particularly, to a housing structure of an acoustic controller that makes the controller usable both in a stationarily placed state and in a rack-mounted state.
2. Description of the Related Art
Conventionally, there has been known an acoustic controller such as a mixer apparatus that can be used both in a state stationarily placed on a flat surface such as tabletop surface, desktop surface, and floor surface and in a state mounted on a rack. Since there are disposed circuit boards or other heat generating component parts in an acoustic controller housing, the interior of the housing must be cooled.
Japanese Design Registration No. 1256520, for example, discloses an acoustic controller in which heat radiation openings are formed in side walls of the housing for cooling the interior of the housing. Also known is an acoustic controller having heat radiation openings formed in a bottom surface of the housing.
Japanese Patent Publication No. 3815559 discloses an acoustic controller (electronic apparatus) having intake ports formed in front and rear surfaces of a metallic housing (casing), circuit boards disposed vertically inside a rear part of the housing, and exhaust ports formed in an upper rear surface of the housing. When the acoustic controller is in a stationarily placed state, an air flow is generated flowing from the intake ports to the exhaust ports, whereby the circuit boards are cooled.
The acoustic controller disclosed in Japanese Design Registration No. 1256520, however, has a drawback that the efficiency of heat radiation becomes low when rack-mounted because of a small distance from the heat radiation openings of the housing to side walls of the rack. The above described prior art acoustic controller having heat radiation openings formed in the housing bottom surface also has a drawback that heat radiation efficiency is lowered when the controller is stationarily placed on a tabletop surface so that the distance between the heat radiation openings and the tabletop surface decreases.
The acoustic controller disclosed in Japanese Patent Publication No. 3815559 has its housing having a large height (thickness) especially at the rear part thereof. If a lower part (lower case) of the controller housing is formed by a resin, such a resin lower case provides a smaller rigidity than that of a metal lower case. Besides, the resin lower case must be provided with thickened portions such as reinforcement ribs and bosses for mounting an upper unit (upper casing part) and circuit boards thereon. In the case of the lower case being large in thickness, the thickened portions formed therein become large in height, which can worsen the moldability of the lower case. Generally, a mixer apparatus is made larger in height at its rear part than at a front part thereof to improve the user's operability. In the acoustic controller disclosed in Japanese Patent Publication No. 3815559 having the circuit boards vertically disposed, the thickened portions formed at the rear part of the controller are noticeably large in height, which is disadvantageous in improving the moldability and poses a problem.